I was making significant progress on my Rex Cancer Center mural until I got to the background colors. That's when confusion set in. Glaze is not like paint. You can't make it a little lighter or a little darker. The only way out of this kind of uncertainty is to test and compare the results.
I quickly did the two-color sketches below. I used two different blues and three different greens. I'm happy with both of the blues; the one on the top tile feels a bit more magical, while the one on the bottom is a bit more true to the North Carolina sky. I'll be using the lighter of the three greens I've tested. The dark green in the top tile is too dark, and the darker green in the bottom tile is too flat, meaning there's no variation in color. I'm going with the lighter color that will be darker where thinner and lighter where the application is thicker. I also like that it has an orangy brown halo around the outer edges.
To better understand how the glaze fires, I used it on a few tiles and plates. I wanted to see the difference between painting the glaze on (the plates) and applying it using a slip trailer (the art tiles).
Using a slip trailer I applied the glaze the way you would decorating cookies with royal icing.
Achieving an even application with a paint brush is harder, but I don’t find the variation unappealing.